Maybe there is nothing wrong with the V200 at all ..
Perhaps it's the way your trying to fly it ?
I'm not saying your a bad pilot, but more maybe you need to adjust the way you fly it.
I know it was a big change for me going from one type of Heli to another.
The flight characteristics of a FB Heli are quiet different from a FBL Heli, until you get used to it.
A FBL Heli is much more agile, requiring very small stick inputs, but a much faster reaction time to correct it.
Then you add the 3in1 unit trying to counter your controls at the same time to balance it out and so on.
Put some training gear on the V200, to help counter any roll/flip from rotorwash or overcorrecting stick inputs.
Keep it lower to the ground (1-2ft) until you can hold it in a steady hover.
Don't try to fly it like your a Pro and take it slow and easy.
Trying to rush it will simply result in more spare parts. (I know, I spent $100 or more in spares the 1st month I owned one)
I went through about 10 main gears in a month, but at the same time I ran them down so flat that the motor gear had almost nothing to grip into.
If I had changed them out after every crash, I bet I would have thrown out 30 or more gears.
All I am trying to say is "Dont Give Up" on the V200 .. There are hundreds of reasons as to why you may be having problems ..
As for changing the Head to FB and the other RX ..
This would be a step backwards and would be no different to flying the CB180 ..
On top of that the old RX may not be capable of running the V200 motors (I dont know for sure, I have never looked into the specs)
If they are higher power rating than the RX is rated, you may end up just burning it out.
Again: .. Put Training Gear On It .. Dont Give Up .. Take It Slow ..
1. Turn on TX and set all but Throttle Trim to 50% (Throttle 0%) - Use Dual Rates to cut back stick inputs even further if you want to tame it down more.
2. Sit the V200 on flat level surface and plug in battery.
3. Don't move the V200, or the sticks until it is initialized. (even the slightest movement can throw the 3in1 Gyro out)
4. Throttle up to just before lift of RPM (about 50%) and as it gets light give it more Throttle (70%) to lift off.
5. Do Not move the sticks during Throttle Up / Lift Off. (This can confuse the 3in1 resulting in auto overcorrection)
6. Do Not let the Heli sit on the ground for more than a couple seconds once light on the skids. (again this can confuse the gyro as its not getting the required feedback from auto corrections)
7. Once in the air, keep it low (1-2ft) so that if the Heli is not responding how you want it, you can get it down with much less "doom" happening.
I hope you don't take this post the wrong way ..
I do know how you feal, as I have been there myself ..
Good luck and keep us informed of your progress